September in Idaho Falls averages a daily high of 24.4°C with nights around 7.3°C. Expect roughly 5.3 wet days totalling 29.4mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit Idaho Falls is June.
Based on IDAHO FALLS KIFI, ID US (5.5km), 1995–2024. 23 years of September data.